Veterinary Diagnostics
As veterinarians, we are faced with a situation that is truly unique in the medical community. Patients come to us who are sick, but they cannot tell us about their illness. In essence, we are neonatal paediatricians. We have to rely on an owner, zoo keeper, etc., to care for and feed their animals for important information. Sometimes the information we get is biased or wrong, leading us down the wrong path. As a result, diagnostic tests are crucial to our diagnosis.
Fortunately, for most species, diagnostic tests have been refined to the point that they allow us to get a clear picture of the inner workings of animals. This has dramatically improved the diagnostic process and even allowed us to detect diseases long before symptoms become apparent. Many pets don’t live long in relation to people, so the ability to diagnose problems before they become firmly established is an important axiom in the way we care for pets at Long Beach Animal Hospital.
We have a page on how to do a home exam to help you catch problems early so they can be treated in a timely manner. This also confirms the need for routine annual wellness exams, especially for middle-aged and older pets. Read these pages so you are not one of the unfortunate pet owners we see too often who have pets that get sick and die prematurely when something could have been done to prevent this.
1. Blood panel
A crucial set of tests to determine if an animal is sick is a blood panel. This panel gives us an indication of the internal health of a pet and allows us to monitor disease processes and treatments. It should be understood that each individual lab has its own set of normal values, which are based on that old static, bell-shaped curve that we all learned to love (and hate) in school. These sets of normals for each laboratory are called reference values.
As a general rule of thumb, if one of your pet’s values is outside the range for this lab, it could mean something is wrong with your pet on that specific test, but not necessarily. In contrast, a normal test of a specific organ on a blood panel, for example a liver enzyme test, does not guarantee that the liver is healthy.
Note that the blood test was taken at a specific time and that the same sample taken hours or days later may have different values. This is why we often need to follow the blood panel over a time series to see which direction the trends are going. This gives us a much better idea of the importance of an abnormal test. Lastly, we do not interpret the blood panels themselves, we use all the information we have available in regards to the diagnostic process. This includes:
- Signage: age, race and gender
- History- What symptoms of illness is a pet displaying?
- Physical exam: the results of a physical exam
- Diagnostic tests: the results of the tests that are run.
- Response to treatment: whether or not a pet responds to treatment for that suspected disease.
The first part of the blood panel is called the CBC, which stands for complete blood count. It is a measure of the white blood cells (WBC) and the red blood cells (RBC) of an animal. When measuring red blood cells, we look for a low count, called anemia, and a high count, called polycythemia.
2. Urine analysis
This test is used in conjunction with the standard blood panel. Its main objective is to evaluate the urinary tract (kidneys, ureters and urinary bladder). It detects inflammation, infection, specific diseases (sugar diabetes) and kidney function. It is obtained in our hospital and sent to the same laboratory that does our standard blood test. Results are also available within 12-24 hours.
3. Faecal analysis
A fecal exam for worms (internal parasites) is a test that we perform many times a day. The microscope comes into play again. Some fresh stool is placed on a slide that already has sterile saline on it. What we are looking for is the parasite’s egg, not the actual parasite, as the parasite resides in the stomach and intestines, and generally does not come out in the stool (tapeworms and the occasional roundworm are an exception). This is called a direct smear.
To further improve our ability to find these eggs, we use a technique called fecal flotation. Taking another sample of fresh stool, we put it in a solution that makes all the eggs (sometimes with the exception of the tapeworm eggs) float to the top. These eggs are then collected with a coverslip and placed on a slide for analysis under the microscope.
In both direct smear and faecal flotation techniques, finding these eggs is a hit or miss method, and it all depends on whether the individual female parasite is shedding eggs at the time of sampling. This means that a negative faecal report does not guarantee that our pet is free of internal parasites.
If we suspect them, we will recheck the stool sample, sometimes several times. By rechecking, we increase the chances that we are testing a sample in which the female parasite residing in the digestive tract is actually releasing eggs into the environment through faeces. Some parasites, particularly Giardia, can be difficult to find on faecal analysis. There are special tests that the laboratory will do on the stool to detect this if we suspect it.
4. Skin scraping
Skin disease is the number one problem we face. Although allergies are the most common cause, pets can also get external parasites (called ectoparasites) that cause skin problems. With the exception of fleas, these parasites are almost always microscopic in size and are diagnosed by scraping the skin.
In this test, a small amount of skin is scraped off as if shaving an area. Since some of the parasites penetrate the outer layers of the skin, the scraping must be done deep enough to cause a small amount of irritation. The discharge is observed under the microscope to look for the parasite itself or for the parasite’s eggs. We have pages on sarcoptic mange and demodectic mange, the two ectoparasites commonly diagnosed with a skin scrape.
5. Ultrasound
When a significant disease process is present, we occasionally need the help of an ultrasound. This is the use of sound waves instead of X-rays to look at internal organs. It is used only when one of our doctors deems it necessary. It allows us to look at an internal organ in a way that X-rays cannot, and it even allows us to biopsy these organs with a small biopsy needle during the ultrasound process. This test must be arranged in advance as we call a specialist to perform the test at our hospital.
Ultrasound has revolutionized the diagnosis of problems in the abdomen in many cases. If we suspected abdominal disease that required surgery prior to the ultrasound, we had to rely only on x-rays or do exploratory surgery to know for sure. With ultrasound, any suspected radiographic problem can now be confirmed, and even further delineated, before any surgery. This has reduced the need for unnecessary surgeries to confirm a diagnosis.
6. Special proofs
Sometimes we need a very specialized test. Fortunately, here in Southern California, we have the expertise to perform one of these tests. The next test, called a scan, is one of those special tests done in our area. It was used to confirm the diagnosis of a hepatic shunt (also called a hepatic shunt or PSS-portosystemic shunt).
7. Histopathology
When we perform surgery or necropsy or take a biopsy of a lesion, we put the sample in formalin to be preserved for microscopic analysis by a pathologist. This is one of the most crucial steps in determining what the lesion is, if it is benign or malignant and if we remove it completely.
